Steel-mixing process.



No. 807,027. PATBNTED DEC. 12, 1905. P. L. T. HB'ROULT.

STEEL MIXING PROCESS.

APPLICATION FILED APR. 19, 1905.

WITNESSES: //A I VVEIVTOR:

UNITED STATES PATENT oFFIoE.

PAUL LOUIS TOUSSAINT'HEROULT, OF LA PRAZ, FRANCE.

STEELFMIXING PROCESS- Specification of Letters Patent.

Patented Dec. 12, 1905.

Applicationfiled April 19, 1905- Serial No. 256,365.

To all whom, it may concern.-

Be it known that I, PAUL LOUIS TOUSSAINT HEROULT, acitizen of theRepublic of France, residing at La Praz, Savoie, France, have inventedcertain new and useful Improvements in Steel-MixingTProcesses, of whichthe following is a specification.

For numerous reasons it is desirable in the steel industry to regulatethe Work so as to secure uniformity of composition and to employ anapparatus having similar functions to those exercised by the mixer whichis used for cast-iron. It has not been found practicable up to thepresent time to use such a mixer because of the changes of compositionof the bath of steel inherent in the method of heating. This heating hasalways been oxidizing, and consequently oxidizes the slag and burns thesilicon, manganese, and carbon of the bath, so that the time and skillof the operator of the apparatus become factors of such importance as tomake the process impracticable.

The process of the present invention makes possible the use of a mixerfor steel preferably purified and deoxidized, substantially as usual inaBessemer converter or other steelmaking apparatus, said mixer being ofconsiderable capacity, economical, and which not only secures uniformityin the product of an entire factory or a number of apparatus, but alsosecuresacertain desulfuration and recarburation and conserves theoxidizable additionssuch.as silicon, manganese, and the likeso as toreduce the quantities of these additions employed to a minimum. Byreason of the resting of the metal atahigh temperature and in very fluidcondition the oxids of silicon and manganese rise to the surface,leaving a clear product.

The heat from an electric current has the prime advantage over theflames or other oxidizing methods of heating previously suggested thatit is non-oxidizing. Preferably there is also maintained in themixing-receptacle a non-oxidizing atmosphere by theintroduction of anoxygen-free gassuch, for example, as producer-gas. By this neutral orreducing atmosphere the slag is maintained deoxidized, so as to favorthe-desulfuration of the metal and assure theconservation of theoxidizable additions referred to.

The mixer is closed, excepting only openings necessary for the repair ofthe linings, the entrance and discharge of the melted metal and of theslag, and for the passage for the electrodes. The aperture through whichthe electrodes pass is preferably made tight by a water-cooledpressure-gasket. The openings for the doors may be made tight in anysuitable way. Furthermore, the atmosphere within the furnace ismaintained under pressure by the gas introduced for this purpose from aproducer. Consequently when there is an opening, either accidental orintentional, at one or more of the doors there is no admission of anyoxidizing element; but there is an emission at such pointof a jet offlame, the extent of which can be controlled.

In the operation of an electric steel-furnace'such, for example, as theHroult oscillating furnace shown in Patent No. 7 07,7 7 6, of

August 26, 1902a certain part of the energy is employed in melting or inraising the temperature of the steel already melted. The remainder isemployed in compensating for the losses in radiation and convection.This fact being granted, it is apparent that by increasing the lineardimensions of the furnace (in each direction) the capacity will beincreased to the third power, while the losses of heat will increaseonly according to the second power, according to the surface exposed.The largest charge ever smelted in an electric furnace, as far as I amaware, has been about four and one-half tons. It is proposed to makethis mixer large enough to carry a charge of three or four hundred tons,to be fed by five or six Bessemer or Siemens- Martin furnaces. There arecertain losses occurring in transferring the metal from the Bessemer orSiemens-Martin furnace to the electric furnace; but it is practicabletocompensate for these losses very cheaply and to supply a suflicientquantity of heat for the reactions proposed, such as deoxidation anddesulfuration. The difiiculties to be met with in carrying out such amixing operation for steel are not to be anticipated by a knowledge ofthe process of mixing pig-iron. The temperature of liquefaction of thepig-iron is about 1050 centigrade, while that of steel is 1600 to 1800centigrade. With pig-iron it is only necessary to pour in fresh ironfrom the blast-furnace at sufficient intervals in order to maintain themass in the mixer in a liquid state; but with steel it is necessary tosupply additional heat, and the difliculties incidental to such aprocess have so far proved prohibitive. For example, an apparatussimilar to that previously referred to, but larger and having a and anendless worm controlled by an electric capacity of one hundred tons,will require in order to maintain its temperature at that of the fusionof steel about fifteen hundred horse-power. If two thousand five hundredhorse-power is furnished to the apparatus, there will remain onethousand horse-power, producing six hundred and thirty-five calories perhorse-power, which places at the disposal of the bath of steel sixhundred and thirty-five thousand calories per hour. The specific heat ofsteel being about 0.25, said quantity of heat is capable of reheatingthrough 100 for an hour about twenty-five tons of steel, which wesuppose to have been furnished to the mixer at a temperature alreadysuflicient or nearly sufficient for tapping.

Instead of attaching only a secondary importance, as is the case inordinary electric furnaces, to the shape of the furnace, as it bears onthe losses of heat by radiation and convection, in this mixer it ispreferred to approach the form presenting the least possible surface. Asthe thickness of the insulating materials will be likewise increased,the caloric effect will be sensibly better than that indicated.

A one-hundred-ton furnace capable of reheating through 100 twenty-fivetons for an hour or of reheating through 50 fifty tons for an hour fedby a two-thousand-five-hundred horse-power generator should preferablyhave about the following dimensions: surface of the bath, twenty-sixsquare meters; depth, one meter. The electrodes, using a single-phasecurrent, may be about ninety-five centimeters square in cross-section byfive meters high, so as to assure their lasting six or seven weeks. Witha three-phase current,

' using three electrodes, the cross-section should be proportionallyreduced.

For the operation above described one hundred kilograms of coal may begasified in the producer connected to the furnace. The mixer ispreferably an oscillating apparatus, soast to permit partial pouring outof the bath. I may, however, be fixed with tap-holes at successiveheights, or various other constructions may be designed without changingthe principle involved.

By way of example, the accompanying drawings show a receptacle havingthree electrodes and operating with a three-phase alternating currentand in which the mixing may be accomplished.

Figure 1 is a vertical section along the broken line X X of Fig. 2. Fig.2 is a horizontal section.

Referring to the receptacle or furnace illustrated, a crucible a. isclosed by a cover 6, through which pass three electrodes 0 0 0 Each ofthese electrodes is carried by an arm, such as (Z, (or (Z or (Z of whichthe support 6 is in engagement with, and may be raised or lowered bymeans of a system of pinions motor f. Each vertical support 6 is guidedby rolls g between U-shaped members fixed upon the heel of the cruciblewith interposed insulating material. Each carbon or elec: trode isembraced by a collar of metal sheets which is compressed or slackened bymeans of a screw h, operated by a wheel z'through a suitableintermediate system of gearing. The crucible a carries also aspoutj,through which the metal may be poured out when the furnace is inclined.There are three doors is 70 corresponding, respectively, in positionwith the electrodes. The slag is ordinarily poured out of the rear doorsand 70 and the metal out of the front door k. The electrodes aresurrounded by cooled pressure-gaskets Z. The crucible a is also providedwith a passage m in communication with a gas-producer n, from which thegases are led into the crucible a, which in operation is entirelyclosed. The metal and slag ordinarily occupy the positions indicated inFig. 1.-

The crucible a carries curved tracks, which rest upon a suitablepedestal 0, and has its other point of support on the articulated pistonof a hydraulic cylinder g, which is also articulated and which serves todetermine the angle at which the crucible is tipped.

The details are represented more or less diagrammatically. They will befound described and shown more in detail in my previous patent abovereferred to.

It will he understood that the furnace may be operated with a two-phaseor single-phase current or with a continuous current and may have anysuitable number of electrodes different from that indicated.

Various apparatus may be used in carrying out the process, and variousmodifications in thedetails of the process may be made by those skilledin the art without departure from the invention.

What I claim is- 1. In the treatment of steel, the process of mixing theproducts from a number of converters or the like, which consists inintroducing them in a molten condition into a single receptacle, andmaintaining the mass molten in said receptacle by heat from an electriccurrent, removing portions only of the composite molten contents of thereceptacle without entirely emptying the same, and successivelyreplenishing the receptacle with fresh additions, whereby to secureuniformity of product from said number of converters, said process beingcarried on in a non-oxidizing atmosphere, whereby desulfuration andconservation of the oxidizable additions are favored.

2. In the treatment of steel, the process which consists in introducingthe steel, purified and deoxidized substantially as usual, and in amolten condition, into a receptacle, and maintaining it molten and in anon-oxidizing atmosphere, whereby desulfuration and conservation of theoxidizable additions are fa- Vored.

3. In the treatment of steel, the process which consists in introducingthe steel, purified and deoxidized substantially as usual, and in amolten condition, into a closed receptacle, maintaining it molten insaid receptacle, and supplying an oxygen-free gas within the receptacle,whereby desulfuration and conservation of the oxidizable additions arefavored.

4. In the treatment of steel, the process which consists in introducingthe steel in a molten condition into a receptacle, and maintaining itmolten in said receptacle by the heat from an electric current, saidprocess being carried on in a non-oxidizing atmosphere, wherebydesulf'uration and conservation of the oxidizable additions are favored.

In witness whereof I have hereunto signed my name in the presence of twosubscribing witnesses.

I PAUL LOUIS TOUSSAINT HEROULT.

Witnesses:

DOMINGO A. UsINA, FRED WHITE.

